More E-Mails Blocked, Return Path Study Finds

E-mail marketers still need to monitor ISPs' e-mail blocking vigilantly, as the problem has worsened.

Twenty-two percent of permission-based e-mail was blocked by top ISPs in 2004, up 3.3 percent from the second half of 2003, e-mail management firm Return Path, New York, found in a new study.

"The spam market changes every day, and ISPs are changing how they're doing things every day," said Jennifer Wilson, vice president of marketing at Return Path. "You can't look at it once and then forget about it. You have to be monitoring it on an ongoing basis."

Some ISPs are worse than others for corporate e-mailers, Return Path found in its analysis of 50,000 marketing campaigns in 2004. Road Runner blocked the most permission-based e-mails at 35 percent, Mail.com blocked 34 percent and Comcast blocked 31 percent.

EarthLink blocked the fewest at only 5 percent, while primary ISPs Yahoo and MSN blocked 11 percent and 10 percent, respectively. In 2004, AOL improved its delivery accuracy most: It blocked only 9 percent of permission-based e-mails, plunging from 22 percent in 2003.

Blocking for each campaign ranged from a low of 1 percent to a high of 57 percent, and 22 percent on average. For clients of Return Path, which aims to improve deliverability of permission-based e-mail, non-delivery rates fell to 9 percent on average after using the company's services for three months.

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